Predicting the consequences of habitat loss for migratory populations

For many migratory species the area of wintering or breeding habitat is changing or is likely to change as a result of processes such as habitat destruction or global environmental change. I show that the ratio of population decline to loss of typical wintering habitat equals d'/(d'+b'), where d' is the slope of relation between per capita winter mortality and population density and b' is the slope of the relation between per capita net breeding output and population density. Similarly the ratio of population decline to loss of typical breeding habitat equals b'/(b'+d'). Game theory models can be used to predict the values of b' and d'. For example, incorporating values of d' and b' from such models for the oystercatcher Haematopus ostralegus shows that a loss of 1% of wintering habitat will result in a population decline of 0.69% while a loss of 1% of breeding habitat will result in a population decline of 0.31%.